IIT-JEE-2007-Physics-Paper2

PAPER - II

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7. Positive and negative point charges of equal magnitude are kept at (0, 0, a/2) and (0, 0, -a/2), respectively. The work done by the electric field when another positive point charge is moved from (-a, 0, 0) to (0, a, 0) is

(A) positive

(B) negative

(C) zero

(D) depends on the path connecting the initial and final positions

8. A magnetic field vector B = B0 j- exists in the region a < x < 2a and vector B = -B0 j-, in the region 2a < x < 3a, where B0 is a positive constant. A positive point charge moving with a velocity vector v = v0 i-, where v0 is a positive constant, enters the magnetic field at x = a. The trajectory of the charge in this region can be like,

9. Electrons with de-Broglie wavelength λ fall on the target in an X-ray tube. The cut-off wavelength of the emitted X-rays is

(A) λ0 = 2mcλ2 /h

(B) λ0 = 2h/mc

(C) λ0 = 2m2c2λ3/h2

(D) λ0 = λ

10. STATEMENT-1

If there is no external torque on a body about its center of mass, then the velocity of the center of mass remains constant.

because

STATEMENT-2

The linear momentum of an isolated system remains constant.

(A) Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for statement-1.

(B) Statement-1 is True, Statement-2 is True, Statement-2 is not a correct explanation for statement-1.

(C) Statement-1 is True, Statement-2 is False

(D) Statement-1 is False, Statement-2 is True

11. STATEMENT-1

A cloth covers a table. Some dishes are kept on it. The cloth can be pulled out without dislodging the dishes from the table.

Because

STATEMENT-2

For every action there is an equal and opposite reaction.

(A) Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for statement-1.

(B) Statement-1 is True, Statement-2 is True, Statement-2 is not a correct explanation for statement-1.